A. Molecular Distillation and Fractional Crystallization to Remove Impurities from Mixture Containing Medium and Long Chain Fatty Acid Triglycerides
European patent application 322,027 to Seiden, published June 28, 1989, discloses the preparation of a complex mixture of MML, MLM, LML, MLL, LLL and MMM triglycerides by random rearrangement of tribehenin and commercial grade medium chain triglycerides, as well as the resulting purification of this complex mixture by techniques such as molecular distillation and fractional crystallization.
B. Liquid/Liquid Extraction to Remove Impurities from Glyceride Mixtures
European Patent application 269.904 to Matsumoto et al. published June 8. 1988. discloses a process for refining fats, such as hard butters and cocoa butter-like fats obtained by enzymatically catalyzed transesterification of a medium-melting fraction of palm oil with stearic acid (see Example 1), to remove partial glycerides and/or free fatty acids. The free fatty acids can be removed by liquid/liquid extraction using solvents such as furfural, n-propyl alcohol, propionitrile, hexane, acetone, methanol and ethanol. This liquid/liquid extracted material is then subjected to fractional crystallization with acetone to remove the partial glycerides. This application makes a point that the liquid/liquid extraction and fractional crystallization do not cause a change in the triglyceride composition. See also Feuge et al, "Modification of Vegetable Oils: Purification of Technical Monoglycerides," J. Am. Oil Chem. Soc., Vol. 27 (1950), pp. 117-22 (removal of residual glycerol from a mixture containing monoglycerides by extraction with hexane); U.S. Pat. No. 2,268,786 to Van Dijck, issued Jan. 6, 1942 (removal of undesirable constituents such as free fatty acids from fat/oils by adding a base such as ammonia to neutralize the free fatty acids and then removal of the soap by countercurrent extraction with a suitable solvent such as ethanol); Rzhekhin et al, "Use of Liquid-Liquid Countercurrent Extraction for Separation of Cottonseed Oil Glycerides from Associated Products and Fractionating Them into Components," Maslob-Zhiv Prom. Vol. 29 (1963), pp. 3-6 (liquid-liquid fractionation of cottonseed oil with ligroine/ethanol/water mixtures to remove nonglycerides from glycerides).
C. Liquid/Liquid Extraction of Coconut Oil with Ethanol
Fish et al, "The Application of Liquid/Liquid Extraction to the Fractionation of Coconut Oil", Oil & Soap (1945), pp. 217-19, discloses the use of liquid/liquid extraction to fractionate coconut oil into 32 fractions, including the final raffinate. The solvent used in this liquid/liquid extraction was 95% ethanol/water.
D. Solvent Extraction of Fats/Oils Using Supercritical Fluids
U.S. Pat. No. 4,504,503 to Biernoth et al. issued Mar. 12, 1985. discloses a process for producing a mixture of triglycerides having butter-like properties by extracting a fat such as butter oil or palm kernel stearin containing triglycerides having a carbon number ranging from 24 to 42 with a supercritical fluid, such as supercritical CO.sub.2, to form: (1) a fraction enriched in triglycerides having said carbon numbers; and (2) a fraction enriched in triglycerides having carbon numbers higher than 42. This fractionation is apparently carried out as a single stage separation. See also Mathias et al, "Phase Equilibria for Supercritical Extraction of Lemon Flavors and Palm Oils with Carbon Dioxide," Fluid Phase Equilibria. Vol. 29 (1986), pp. 545-54, which discloses the extraction of palm oil with supercritical CO.sub.2 to obtain a concentration of triglycerides in the middle range of carbon numbers,.e.g. 36.
E. Liquid/Liquid Extraction of Oils or Complex Lipid Mixtures with Multiple Solvent Systems that Contain Ethanol or Methanol
U.S. Pat. No. 2.651.646 to Goldsmith. issued Sept. 8, 1953. discloses a method for increasing the level of monoglycerides in a mixture of glycerides by liquid/liquid extraction using a two-phase solvent system comprising an aqueous lower aliphatic alcohol (e.g., methanol or ethanol) and a hydrocarbon which is immiscible with the aqueous alcohol phase (e.g., hexane). See also Therriault, "Fractionation of Lipids by Countercurrent Distribution," J. Am. Oil Chem. Soc., Vol. 40 (1963), pp. 394-99, which discloses countercurrent liquid/liquid extraction of a mixture of triglyceride, monoglyceride, cholesterol and stearic acid using a two-phase solvent system consisting of hexane, methanol, chloroform and water.